The present application relates to heavy vehicle air braking systems, and is particularly directed to a valve module for an air braking system of a heavy vehicle, such as a truck.
A typical air braking system includes an anti-lock brake system (ABS) that has a number of ABS modulator valves. The ABS modulator valves are controlled in response to electrical control signals from an ABS controller to modulate air flow to service brake chambers to prevent locking of braked wheels to improve the braking characteristics of the heavy vehicle. The ABS modulator valves in some heavy vehicles are controlled to control not only an anti-lock braking event, but also to control other types of autonomous braking events that are auxiliary to the normal service braking function of the heavy vehicle. An example autonomous braking event that is auxiliary to the normal service braking function comprises hill start assist (HSA). HSA prevents rolling back of the heavy vehicle when the vehicle is stationary on an uphill incline and the foot of the vehicle driver is transitioning from the vehicle foot brake pedal to the vehicle foot accelerator pedal to accelerate the vehicle from its stationary position on the uphill incline. It would be desirable to improve performance of autonomous braking events, such as HSA, in heavy vehicles.